Bidirectional LED light string

ABSTRACT

Disclosed is a rectifierless light string that uses bidirectional LEDs. Each LED is illuminated on both the positive and the negative portion of an AC signal so that the AC signal does not have to be rectified. In addition, LEDs are mounted on LED holder plugs, which are designed to allow the LEDs and bypass resistors to be automatically inserted in the LED holder plug. The LED holder plugs are inserted into a light string socket that contains a shunt switch that provides a conduction path when the LED holder plug is not firmly inserted in the light string socket. In this manner, conduction can occur in the light string when the LED holder plug is dislodged.

BACKGROUND

Light emitting diodes (LEDs) have played an important role in thelighting industry. LEDs use considerably less energy than incandescentbulbs. Further, LEDs are less expensive to manufacture. LEDs also have along lifetime, which reduces the necessity and expense of changingbulbs. In typical use situations, an LED may have a lifetime of 50,000hours, whereas an incandescent bulb may have a lifetime of 1,000 to2,000 hours. Accordingly, the convenience of using LED bulbs is great,as well as the cost savings involved with the use of LED bulbs.

SUMMARY

An embodiment of the present invention may therefore comprise seriallight emitting diode light string that does not use a rectifiercomprising: a plurality of bidirectional light emitting diodes, each ofthe plurality of bidirectional light emitting diodes comprising: a firstlight emitting diode mounted on a first wafer that is encapsulated by alens, the first light emitting diode having an anode and a cathode; asecond light emitting diode mounted on a second wafer that isencapsulated by the lens, the second light emitting diode having ananode that is electrically connected to the cathode of the first lightemitting diode to form a first node and a cathode that is electricallyconnected to the anode of the first light emitting diode to form asecond node; a serial string of the plurality of bidirectional lightemitting diodes formed by connecting the first nodes of each of theplurality of light emitting diodes to the second node of another of theplurality of bidirectional light emitting diodes; an alternating currentconnector attached to the serial string of bidirectional light emittingdiodes to form the light emitting diode light string, the alternatingcurrent connector providing alternating current to the serial string ofbidirectional light emitting diodes, without a rectifier, which causesthe first light emitting diode to be illuminated while the alternatingcurrent is positive, and which causes the second light emitting diode tobe illuminated while the alternating current is negative, so that thebidirectional light emitting diodes do not flicker and have an extendedlife, since each of the first light emitting diode and the second lightemitting diode is illuminated for a half of a cycle of the alternatingcurrent.

An embodiment of the present invention may further comprise lightemitting diode connector assembly comprising: a light string sockethaving a central cavity; wire lead connectors attached to the lightstring socket that attach to light string wires of a light string; alight emitting diode plug that has a size and shape to fit firmly in thecentral cavity of the light string socket, the light emitting diode plughaving a central cavity and constructed to allow leads of a resistivecircuit component and leads of a light emitting diode to be insertedthrough the light emitting diode plug and wrapped around an exteriorportion of the light emitting diode plug; light string contacts disposedin the central cavity of the light string socket on an inner surface ofthe light string socket, which are aligned with the leads of theresistive element and the leads of the light emitting diode, that arewrapped around an outer surface of the light string socket, so that theleads of the resistive element and the leads of the light emitting diodeelectrically connect to the light string contacts when the lightemitting diode holder plug is inserted in the light string socket; ashunt switch that is electrically connected to the light stringcontacts; a switch disconnect shaft disposed on the light emitting diodeholder plug that engages the shunt switch and separates spring arms ofthe shunt switch when the light emitting diode holder plug is fullyinserted in the light string socket so that the shunt switch is open;the resistive component providing an alternative current path around thelight emitting diode whenever the light emitting diode is burned out andthe shunt switch providing an alternative current path in the lightstring socket whenever the light emitting diode holder plug is dislodgedfrom the light string socket.

An embodiment of the present invention may further comprise a method ofattaching a light emitting diode to a light string comprising: securingthe light emitting diode to a light emitting diode holder plug;inserting leads of the light emitting diode in an automated fashionthrough a central portion of the light emitting diode holder plug andwrapping the leads of the light emitting diode around an outer surfaceof the light emitting diode holder plug; inserting leads of a resistivecomponent through the light emitting diode holder plug in an automatedfashion and wrapping the leads of the resistive component around anouter surface of the light emitting diode holder plug; providing a lightstring socket that is electrically connected to wires of the lightstring, the light string socket having light string contacts on aninterior portion of the light string socket that are aligned with theleads of the light emitting diode and the leads of the resistivecomponent when the light emitting diode holder plug is inserted into thelight string socket so that the resistive component provides analternative current path whenever the light emitting diode is burned outand the light emitting diode plug is inserted in the light stringsocket; providing a shunt switch that is electrically connected to thelight string contacts and is disposed in the light string socket so thatthe light string contacts are electrically connected whenever the lightemitting diode holder plug is dislodged from the light string socket;opening the shunt switch when the light emitting diode holder plug isinserted in the light string socket so that the shunt switch does notprovide a current path for the light string when the light emittingdiode holder plug is inserted in the light string socket and currentflows through the light emitting diode or the resistive element.

An embodiment of the present invention may further comprise a seriallight emitting diode light string that does not use a rectifiercomprising: a plurality of bidirectional light emitting diodes, each ofthe plurality of bidirectional light emitting diodes comprising: a firstlight emitting diode mounted on a first wafer that is encapsulated by alens, the first light emitting diode having an anode and a cathode; asecond light emitting diode mounted on a second wafer that isencapsulated by the lens, the second light emitting diode having ananode that is electrically connected to the cathode of the first lightemitting diode to form a first node and a cathode that is electricallyconnected to the anode of the first light emitting diode to form asecond node; a serial string of the plurality of bidirectional lightemitting diodes formed by connecting the first nodes of each of theplurality of light emitting diodes to the second node of another of theplurality of bidirectional light emitting diodes; an alternating currentconnector attached to the serial string of bidirectional light emittingdiodes to form the light emitting diode light string, the alternatingcurrent connector providing alternating current to the serial string ofbidirectional light emitting diodes, without a rectifier, which causesthe first light emitting diode to be illuminated while the alternatingcurrent is positive, and which causes the second light emitting diode tobe illuminated while the alternating current is negative, so that thebidirectional light emitting diodes do not flicker and have an extendedlife, since each of the first light emitting diode and the second lightemitting diode is illuminated for a half of a cycle of the alternatingcurrent; a light emitting diode connector assembly for mounting andconnecting the plurality of bidirectional light emitting diodes to formthe serial string of the plurality of bidirectional light emittingdiodes comprising: a light string socket having a central cavity; wirelead connectors attached to the light string socket that attach to lightstring wires of a light string; a light emitting diode plug that has asize and shape to fit firmly in the central cavity of the light stringsocket, the light emitting diode plug having a central cavity andconstructed to allow leads of a resistive circuit component and leads ofa light emitting diode to be inserted through the light emitting diodeplug and wrapped around an exterior portion of the light emitting diodeplug; light string contacts disposed in the central cavity of the lightstring socket on an inner surface of the light string socket, which arealigned with the leads of the resistive element and the leads of thelight emitting diode, that are wrapped around an outer surface of thelight string socket, so that the leads of the resistive element and theleads of the light emitting diode electrically connect to the lightstring contacts when the light emitting diode holder plug is inserted inthe light string socket; a shunt switch that is electrically connectedto the light string contacts; a switch disconnect shaft disposed on thelight emitting diode holder plug that engages the shunt switch andseparates spring arms of the shunt switch when the light emitting diodeholder plug is fully inserted in the light string socket so that theshunt switch is open; the resistive component providing an alternativecurrent path around the light emitting diode whenever the light emittingdiode is burned out and the shunt switch providing an alternativecurrent path in the light string socket whenever the light emittingdiode holder plug is dislodged from the light string socket.

An embodiment of the present invention may further comprise a method ofmaking a serial light emitting diode light string that does not use arectifier comprising: providing a plurality of bidirectional lightemitting diodes, each of the plurality of bidirectional light emittingdiodes comprising: a first light emitting diode mounted on a first waferthat is encapsulated by a lens, the first light emitting diode having ananode and a cathode; a second light emitting diode mounted on a secondwafer that is encapsulated by the lens, the second light emitting diodehaving an anode that is electrically connected to the cathode of thefirst light emitting diode to form a first node and a cathode that iselectrically connected to the anode of the first light emitting diode toform a second node; connecting the plurality of bidirectional lightemitting diodes to the serial light emitting diode light string so thatthe first nodes are connected to the second nodes to form a serialstring of bidirectional light emitting diodes, comprising: securing thelight emitting diode to a light emitting diode holder plug; insertingleads of the light emitting diode in an automated fashion through acentral portion of the light emitting diode holder plug and wrapping theleads of the light emitting diode around an outer surface of the lightemitting diode holder plug; inserting leads of a resistive componentthrough the light emitting diode holder plug in an automated fashion andwrapping the leads of the resistive component around an outer surface ofthe light emitting diode holder plug; providing a light string socketthat is electrically connected to wires of the light string, the lightstring socket having light string contacts on an interior portion of thelight string socket that are aligned with the leads of the lightemitting diode and the leads of the resistive component when the lightemitting diode holder plug is inserted into the light string socket sothat the resistive component provides an alternative current pathwhenever the light emitting diode is burned out and the light emittingdiode plug is inserted in the light string socket; a shunt switch thatis electrically connected to the light string contacts and is disposedin the light string socket so that the light string contacts areelectrically connected whenever the light emitting diode holder plug isdislodged from the light string socket; opening the shunt switch whenthe light emitting diode holder plug is inserted in the light stringsocket so that the shunt switch does not provide a current path for thelight string when the light emitting diode holder plug is inserted inthe light string socket and current flows through the light emittingdiode or the resistive element; applying an alternating current to theserial string of bidirectional light emitting diodes without rectifyingthe alternating current which causes the first light emitting diode toilluminate when the alternating current is positive, and causes thesecond light emitting diode to illuminate when the alternating currentis negative, so that the bidirectional light emitting diodes do notflicker and have an extended life since each of the first light emittingdiode and the second light emitting diode are illuminated for a halfcycle of the alternating current.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an embodiment of a bidirectional LED light string.

FIG. 2 is an embodiment of a bidirectional LED.

FIG. 3 is a circuit diagram of an embodiment of an implementation of abidirectional LED in a light string.

FIG. 4 is a sectional view of an embodiment of an LED holder plug.

FIG. 5 is an embodiment of a light string socket.

FIG. 6 is an embodiment of an LED holder plug having a shunt resistordisposed in the LED holder plug.

FIG. 7 is a sectional view of an embodiment of a light string socket.

FIG. 8 is a sectional view of an embodiment of an LED light connectorassembly.

FIG. 9 is a schematic top view of an embodiment of a bidirectional LED.

FIG. 10 is a side view of an embodiment of a bidirectional LED.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a pictorial circuit diagram of an embodiment of abidirectional LED light string. As shown in FIG. 1, plug 102 is adaptedto be plugged into a wall socket having an AC signal. A standard wallsocket carries 117 volts RMS on a standard sinusoidal electric powersignal. The circuit illustrated in FIG. 1 does not require a rectifierthat rectifies the signal to create either a half wave signal or a fullwave rectified signal, as explained below.

Each of the LEDs 104, 106, 108, 110, 112, 114 comprise bidirectionalLEDs that are two LEDs connected in parallel in opposite polarizationdirections, as shown in FIG. 2, in more detail. By using bidirectionalLEDs, one of the LEDs will activate during the positive portion of thesinusoidal AC signal, while the other LED will activate during thenegative portion of the sinusoidal AC signal. As such, at least one ofthe two bidirectional LEDs is lit at substantially all times. Thiseliminates the flickering that can occur when an AC signal is applied toa single LED and the flickering that occurs as a result of half-waverectification. Of course, to eliminate flickering using a standard LED,a full-wave rectifier can be used, together with other components, suchas capacitors, resistors, and inductors, to provide a substantially DCsignal that does not vary substantially in magnitude and does not createflickering using non-bidirectional LEDs. However, rectifiers can beexpensive when compared to the other components of an LED light stringand add complexity to the light string, so elimination of the rectifiermakes the light strings simpler and less expensive.

Since each of the LEDs in the bidirectional LEDs 104-114 is activatedduring a half cycle, the light string has a lifetime that is double thelifetime of a single LED in a light string having a fully rectifiedsinusoidal signal because the LEDs in the bidirectional LED areilluminated for only half of a cycle. As such, rectifiers can beeliminated from the light string circuitry when bidirectional LEDs areused. Each of the LEDs in the bidirectional LED combination typicallycause a voltage drop of about 2.2 volts when a 117 volt RMS AC signal isapplied to the light string. The voltage drop across each of the LEDs ina string of serially connected LEDs is caused by the impedance of theLEDs when an AC signal is applied to the circuit. Impedance (Z) is thecombination of the resistance (R) plus the reactance (X) of the LED.LEDs have virtually no resistance but have a reactance sufficient tocause the voltage drop of typically about 2.2 volts when a desiredoperating current flows through the LEDs in the LED serially connectedlight string. LEDs are efficient light sources, since the resistance ofthe LEDs is virtually zero. The voltage drop of a typical LED of about2.2 volts at a desired operating current of the LED and a frequency of60 Hz is primarily due to the reactance (X) of the LED. Consequently, ifa sufficient number of LEDs are placed in a serial circuit, a sufficientamount of reactance (X) will be present in the circuit to limit thecurrent flowing through the circuit to an operating current that willnot cause the LEDs to burn out. Of course, it is desirable to also placea resistor that is serially connected in the light string to limit theamount of in-rush current that may occur, since the reactance (X) of theLEDs is primarily a result of the capacitance of the LEDs and notinductance. Hence, it has been determined that the use of apredetermined number of LEDs, based upon the reactance (X) of the LEDsand the frequency of the power signal, provides a proper operatingcurrent for a serially connected light string. As indicated above, arectifier is not required when using bidirectional diodes. The compleximpedance (Z) of the LED is equal to the resistance (R) plus theimaginary portion (jX), which is the imaginary unit j times thereactance (X). If there are less than the optimum number ofbidirectional diodes 104-114, a series resistor will be necessary in thelight string. However, if there are the optimum number of thebidirectional LEDs 104-114, a series resistor in the light string maynot be required, since a full voltage drop can be achieved at areasonable and proper operating current with the impedance provided byeach of the diodes in the bidirectional LEDs utilized in the lightstring 112. The only exception is that a series resistor may bebeneficial to prevent startup current from surging and damaging theLEDs. FIG. 1 also illustrates a socket 116 that can be used to connectthe light string 112 to an additional light string. In that case, apower lead (not shown) is needed to supply power to the subsequent lightstring.

FIG. 2 is a schematic diagram of a bidirectional LED 200. Thebidirectional LED 200 has a first LED 202 that is connected in parallelwith a second LED 204 that is aligned in an opposite direction. Lens 206can be a proxy that directs the light outwardly from the LEDs 202, 204.In some higher powered LEDs, various plastics can be used for the lens206 that function to transmit the light without degradation. Lessexpensive, lower power LEDs may use epoxy for lens 206. Thebidirectional LEDs 200 are connected to leads 208, 210. The leads 208,210 do not comprise either an anode lead or a cathode lead, since thebidirectional LEDs 200 have anodes connected to cathodes and cathodesconnected to anodes. When an AC signal is applied to the bidirectionalLEDs, via leads 208, 210, both LEDs 202, 204 will conduct. When the ACsignal on lead 208 is positive, LED 202 will conduct. When the AC signalapplied to lead 210 is positive, LED 204 will conduct. In other words,when the AC signal on lead 208 is positive, LED 202 will conduct. Whenthe AC signal on lead 208 is negative, LED 204 will conduct. In thismanner, at least one of the LEDs 202, 204 is conducting and emittinglight during the entire AC signal that is applied to leads 208, 210.Accordingly, the bidirectional LED structure 200 shown in FIG. 2, doesnot require rectification of the AC signal, which lowers the overallcost of the system that uses bidirectional LEDs 200. Further, thelongevity of the system is doubled, since only one of the LEDs 202, 204is conducting and lit at any given time when an AC signal is applied toleads 208, 210. As such, the lifetime of the bidirectional LEDs 200 andthe light string is doubled. LEDs may have a lifetime of 50,000 hours.By doubling the lifetime, a bidirectional LED may have a lifetime of100,000 hours. Since the lens 206 encapsulates the bidirectional LEDs200, there is little or no flickering of the light that is emitted bythe lens 206, since one of the LEDs 202, 204 is lit and transmittinglight virtually the entire time that the AC signal is applied to leads208, 210.

FIG. 3 is a circuit diagram 300 of one embodiment of the manner in whicha bidirectional LED 302 can be disposed in a light string. Thebidirectional LED 302 has LED leads 304, 306 that are connected to thelight string. The light string comprises a light string portion 308 andanother light string portion 310. Additional LEDs (not shown) areconnected in series. The LED is disposed in an LED holder plug, asdisclosed in FIGS. 4 and 6, which plugs into a light string socket, asdisclosed in FIGS. 5 and 7. The LED holder plug contains a bypassresistor 312 that can be mounted in the LED holder plug, using automatedtechniques, to connect to the first portion of the light string 308 andthe second portion of the light string 310 when the bidirectional LEDburns out. In this manner, when the elements of the bidirectional LED302 burn out, the resistor 312 will continue to conduct electricity fromthe light string portion 308 to light string portion 310, so that otherseries connected LEDs will continue to be lit and current will continueto flow through the overall light string. In addition, shunt switch 314is disposed in a light string socket, as disclosed below, which receivesthe LED holder plug and provides an open circuit between light stringportion 308 and light string portion 310. If the LED holder plug becomesdislodged from the light string socket, the shunt switch 314 closes toprovide a current path between light string portion 308 and light stringportion 310, so that the light string continues to provide current toother series connected LEDs. In this manner, the circuit 300 of FIG. 3provides a current path for a light string having serially connectedLEDs when either the LEDs burn out or the LED holder plugs becomedislodged.

FIG. 4 is a cross-sectional view of an embodiment of an LED holder plug400. As illustrated in FIG. 4, the LED holder plug 400 has an annularcylinder 406 that forms an open central cavity 404. As shown in FIG. 4,the central cavity 404 provides an opening that extends throughout thecentral portion of the LED holder plug 400. However, in an alternativeembodiment, a lower portion of the annular cylinder 406 may be solid,with the exception of openings for LED lead 408 and LED lead 410. Asshown in the embodiment of FIG. 4, the LED 402 has two leads, LED lead408 and LED lead 410. The LED leads 408, 410 extend through the centralcavity 404 and are wrapped around the annular cylinder 406, so that theLED leads 408, 410 are exposed on the outer surface of the annularcylinder 406. In this manner, when the LED holder plug 400 is insertedinto the light string socket, the LED leads 408, 410 will electricallyconnect to contacts in the light string holder, as disclosed below. Ofcourse, there may be many different shapes for the LED holder plug 400.The LED holder plug 400 is designed to allow LED 402 to be automaticallyinserted in the LED holder plug 400. In addition, the LED holder plug400 may also be constructed to allow a resistor to be automaticallyinserted also, as disclosed in more detail below.

FIG. 5 is a sectional view of a light string socket 500. As illustratedin FIG. 5, the light string socket 500 has an annular socket housing502. Disposed on the inner surface of the annular socket housing 502 islight string contact 504 and light string contact 506. Light stringcontacts 504, 506 are metal contacts that contact the LED leads when theLED holder plug is inserted in the top opening of the light stringsocket 500. Light string contact 504 is connected to the wire connector516 and wire connector 512. In addition, the light string contact 504abuts against the light string wire 508, which may correspond to lightstring portion 308 of FIG. 3. Similarly, light string contact 506 isconnected to wire connector 518 and wire connector 514. Wire connector518 and wire connector 514 are electrically connected to the lightstring wire 510 that may correspond to light string portion 310 of FIG.3. Additionally, light string wire 510 abuts against the light stringcontact 506 to provide a further electrical connection.

The light string socket 500 of FIG. 5 is adapted to receive the LEDholder plug 400 and LED 402 illustrated in FIG. 4. When assembled, theLED leads 408, 410 contact the light string contacts 504, 506,respectively, to complete a circuit from the light string wire 508 tothe light string wire 510.

FIG. 6 is another embodiment of an LED holder plug 600. As shown in FIG.6, the LED holder plug 600 holds an LED 602. The LED 602 has an LED lead604 and an LED lead 606. The LED holder plug 600 has a central cavity607 that extends from the opening for the LED 602 to a bottom platform618. Bottom platform 618 has openings for the LED leads 604, 606 and forthe resistor leads 610, 612. Both the resistor 608 and the LED 602 canbe inserted through the central cavity 607 and the openings in thebottom platform 618 in an automated fashion using a robotic arm or otherwell-known automated inserter devices, which greatly reduces the overallcost of the LED holder plug assembly 620. Once the LED leads 604, 606and the resistor leads 610, 612 are inserted through the openings in thebottom platform 618, the leads are folded around the bottom and theoutside of the annular cylinder 614. This process can also be performedin an automated fashion. In this manner, the resistor leads 610, 612 andthe LED leads 604, 606 are electrically connected to contacts on theinterior portion of a light string socket, such as light string socket700, illustrated in FIG. 7. The bottom platform 618 has a switchdisconnect shaft 616 that interacts with a shunt switch on a lightstring socket, as disclosed in more detail with respect to FIG. 7.

FIG. 7 is a sectional view of a light string socket 700 that iscompatible with the LED holder plug 600 of FIG. 6. The light stringsocket 700 has an annular socket housing 702 that forms a central cavity703. Light string contacts 704, 706 are attached to the inner surface ofthe annular socket housing 702. The light string contacts 704, 706extend along a portion of the length of the central cavity 703. Thelight string contacts 704, 706 are connected to spring arms 720, 722that extend downwardly through the central opening in the annular sockethousing 702. The spring arms 720, 722 are biased together to create acontact between the light string contact 704 and light string contact706. Light string wire 716 and light string wire 718 are electricallyconnected to light string contact 704 and light string contact 706,respectively. Connector 708 is attached to the annular socket housing702 and to the wire connector 712. Similarly, connector 710 is connectedto the annular socket housing 702 and the wire connector 714. Wireconnector 712 holds the light string wire 716 tightly within the annularsocket housing 702. Similarly, wire connector 714 holds the light stringwire 718 firmly within the annular socket housing 702. Wire connectors712, 714 are typically metal wire connectors that provide a goodelectrical connection to light string contacts 704, 706, respectively.The shunt switch 724, which is formed from the spring arm 720 and springarm 722, provides a switch that can electrically connect the lightstring contact 704 and the light string contact 706. Of course, anydesired type of mechanical contact can be used to connect and disconnectan electrical bypass between light string wires 716, 718 when LED holderplug 600 is not present in light string socket 700.

FIG. 8 is a cross-sectional view of an embodiment of an LED lightassembly 800. The LED light assembly 800 comprises an LED 802, an LEDholder plug 804, and a light string socket 806. The LED holder plug 804is similar to the LED holder plug 600 of FIG. 6. Likewise, the lightstring socket 806 is similar to light string socket 700 of FIG. 7. Asillustrated in FIG. 8, the LED holder plug 804 includes a central cavity805. At the bottom of the central cavity 805 is a lower platform 807.Openings are formed in the lower platform 807 so that the resistor wires810, 812 of resistor 808 can be automatically inserted through thebottom portion of the LED holder plug 804 and wrapped around the outersurface of the lower end of the LED holder plug 804. Similarly, the LEDleads 814, 816 of LED 802 can be automatically inserted through openingsin the lower platform 807 and wrapped around the outer surface of theLED holder plug 804, so that the LED leads 814, 816 contact the lightstring contacts 832, 834, respectively. In this manner, both theresistor wire 810 and LED lead 814 have an electrical connection withlight string contact 832. Similarly, resistor wire 812 and LED lead 816electrically connect to the light string contact 834. Connector 818 is ametal connector that secures the light string wire 822 and connects thelight string wire 822 to the light string contact 832. Similarly,connector 820 is a metal connector that firmly holds the light stringwire 824 and provides a connection between the light string contact 834and light string wire 824. As such, a circuit is completed between lightstring wire 822 and light string wire 824 through the resistor 808 andthe LED 802 via light string contacts 832, 834, when the LED holder plug804 is inserted into the light string socket 806.

As also illustrated in FIG. 8, a shunt switch 826 is present andprovides a connection between light string contact 832 and light stringcontact 834 when the LED holder plug 804 is dislodged from light stringsocket 806. As illustrated in FIG. 8, both the resistor 808 and the LED802 provide a circuit path from the light string wire 822 to the lightstring wire 824, as explained above. If the LED 802 burns out, andcreates an open circuit, the resistor 808 provides an alternativecurrent path from the light string wire 822 to the light string wire824. In this manner, other series wired LEDs will not be disconnectedfrom the series circuit. However, if the LED holder plug 804 becomesdislodged from the light string socket 806, resistor 808 will alsobecome disconnected and will not function to complete the circuit fromlight string wire 822 to light string wire 824. Shunt switch 826functions to complete the circuit between the light string wire 822 andthe light string wire 824 when the LED holder plug 804 becomes dislodgedfrom the light string socket 806. As illustrated in FIG. 8, the switchdisconnect shaft 836 extends between the spring arm 828 and spring arm830 and causes the spring arms 828, 830 to separate when the LED holderplug 804 is firmly inserted into the light string socket 806. When theLED holder plug 804 is not firmly and fully inserted in the light stringsocket, the spring arms 720, 722, as illustrated in FIG. 7, connect witheach other to provide a connection between the light string wire 716 andlight string wire 718, as shown in FIG. 7. By causing the shunt switch826 of FIG. 8 to be open by separating the spring arms 828, 830 with theswitch disconnect shaft 836, the current is forced to flow through theLED 802 and/or resistor 808. As such, the shunt switch 826 provides acurrent path to other series connected LED lights on the light stringwhen the LED holder plug 804 is not firmly and fully inserted within thelight string socket 806.

Of course, any type of mechanical contact switch could be used tocomplete the connection between light string wire 822 and light stringwire 824. For example, a simple contact switch at the bottom of the LEDholder plug 804 could be used to open the contact between the lightstring wire 822 and light string wire 824 when the LED holder plug 804is inserted into the light string socket 806. Such a contact switchcould be activated by the lower platform 807 in any desired manner.

FIG. 9 is a schematic top view of a bidirectional LED 900. Asillustrated in FIG. 9, brackets 902, 904 are conductive devices that areconnected to the leads of the bidirectional LED 900. A reflector 918 ismounted on the bracket 904. Semiconductor chips 906, 908 are mountedinside the reflector 918 in opposite directions. Wire 914 connects theanode of chip 908 to bracket 904 while wire 916 connects the cathode ofchip 906 to bracket 904. Wire 912 connects the cathode of chip 908 tobracket 902. Wire 910 connects the anode of chip 906 to bracket 902. Inthis manner, the chips 906, 908 are wired in parallel in oppositedirections and connected to the brackets 902, 904.

FIG. 10 is a side view of the bidirectional LED 900. As illustrated inFIG. 10, brackets 902, 904 protrude from the lower portion of the lens920. The chip 906 is illustrated in the side view of FIG. 10. Chip 908is not illustrated, since chip 908 is blocked by chip 906 in the sideview of FIG. 10. Wires 910, 912, 914, 916 attach the chips 906, 908 (notshown) to the brackets 902, 904. In this manner, bidirectional LEDs canbe placed in a single bidirectional LED 900 within the bracket 904 tocreate a bidirectional LED within a single lens 920.

Hence, embodiments are disclosed that allow LEDs to be inserted in anLED holder plug in an automated fashion, as well as resistors, whichreduces the cost of assembly of an LED light string, such as the lightstring 100 that uses bidirectional LEDs. In this manner, a bypasscomponent, such as a resistor, can be connected in parallel with an LEDso that current can continue to flow in a serially connected lightstring if an LED burns out. Further, a shunt switch can be utilized,which provides an alternative current path around an LED light assemblyif the LED holder plug becomes dislodged or is not firmly seated withinthe light string socket. As such, the current path is establishedbetween the light string wires in each LED light assembly, so thatadditional light assemblies that are connected in series will maintainpower. When bidirectional LEDs are utilized, a rectifier is notrequired, since the bidirectional LED will be lit during both positiveand negative cycles of an AC signal. Further, when a sufficient numberof LEDs are placed in series in the line, an adequate amount ofimpedance can be generated, so that an additional impedance element isnot required. However, if the LED holder plug becomes dislodged in thelight string socket, a shunt switch or contact switch may be activatedthat eliminates the impedance for that particular LED light assembly. Inthat case, resistive elements should be included within the series lightstring to prevent an overcurrent situation in the light string.

The foregoing description of the invention has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise form disclosed, andother modifications and variations may be possible in light of the aboveteachings. The embodiment was chosen and described in order to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and various modifications as are suited to theparticular use contemplated. It is intended that the appended claims beconstrued to include other alternative embodiments of the inventionexcept insofar as limited by the prior art.

What is claimed is:
 1. A serial light emitting diode light string thatdoes not use a rectifier comprising: a plurality of bidirectional lightemitting diodes, each of said plurality of bidirectional light emittingdiodes comprising: a first light emitting diode mounted on a first waferthat is encapsulated by a lens, said first light emitting diode havingan anode and a cathode; a second light emitting diode mounted on asecond wafer that is encapsulated by said lens, said second lightemitting diode having an anode that is electrically connected to saidcathode of said first light emitting diode to form a first node and acathode that is electrically connected to said anode of said first lightemitting diode to form a second node; a serial string of said pluralityof bidirectional light emitting diodes formed by connecting said firstnodes of each bidirectional light emitting diode of said plurality ofbidirectional light emitting diodes to said second nodes of an adjacentbidirectional light emitting diode of said plurality of bidirectionallight emitting diodes to create said serial light emitting diode lightstring; a bypass resistor connected between said first node and saidsecond node of each bidirectional light emitting diode of said pluralityof bidirectional light emitting diodes which provides an alternativecurrent path around each bidirectional light emitting diode of saidplurality of bidirectional light emitting diodes; a shunt switchconnected between said first node and said second node of eachbidirectional light emitting diode of said plurality of bidirectionallight emitting diodes, said shunt switch disposed in a light stringsocket so that when a bidirectional light emitting diode is disconnectedfrom said light string socket, said shunt switch creates a shunt aroundsaid light string socket which provides an alternative current patharound said light string socket for each bidirectional light emittingdiode that becomes disconnected from said light string socket; analternating current connector attached to said serial light emittingdiode light string, said alternating current connector providingalternating current to said serial string of bidirectional lightemitting diodes, without a rectifier, which causes said first lightemitting diode to be illuminated while said alternating current ispositive, and which causes said second light emitting diode to beilluminated while said alternating current is negative, so that saidbidirectional light emitting diodes do not flicker and have an extendedlife, since each of said first light emitting diode and said secondlight emitting diode is illuminated for a half of a cycle of saidalternating current.
 2. The serial light emitting diode light string ofclaim 1 further comprising: a resistive element disposed in said serialstring of bidirectional light emitting diodes that limits current flow.3. A method of making a serial string of bidirectional light emittingdiodes that does not use a rectifier comprising: providing a pluralityof bidirectional light emitting diodes, each of said plurality ofbidirectional light emitting diodes comprising: a first light emittingdiode mounted on a first wafer that is encapsulated by a lens, saidfirst light emitting diode having an anode and a cathode; a second lightemitting diode mounted on a second wafer that is encapsulated by saidlens, said second light emitting diode having an anode that iselectrically connected to said cathode of said first light emittingdiode to form a first node and a cathode that is electrically connectedto said anode of said first light emitting diode to form a second node;connecting said plurality of bidirectional light emitting diodes so thatsaid first nodes of each bidirectional light emitting diode areconnected to said second nodes of adjacent bidirectional light emittingdiodes to form said serial string of bidirectional light emittingdiodes; connecting a bypass resistor between said first node and saidsecond node of each bidirectional light emitting diode of said serialstring of bidirectional light emitting diodes which provides analternative current path around each bidirectional light emitting diodeof said serial string of bidirectional light emitting diodes; connectinga shunt switch between said first node and said second node of eachlight emitting diode of said plurality of bidirectional light emittingdiodes, said shunt switch disposed in a light string socket so that whena bidirectional light emitting diode is disconnected from said lightstring socket, said shunt switch creates a shunt around said lightstring socket which provides an alternative current path around eachlight string socket for each bidirectional light emitting diode thatbecomes disconnected from said light string socket; applying analternating current to said serial string of bidirectional lightemitting diodes without rectifying said alternating current which causessaid first light emitting diode to illuminate when said alternatingcurrent is positive, and causes said second light emitting diode toilluminate when said alternating current is negative, so that saidbidirectional light emitting diodes do not flicker and have an extendedlife since each of said first light emitting diode and said second lightemitting diode are illuminated for a half cycle of said alternatingcurrent.
 4. The method of claim 3 further comprising: connecting aresistive element in said serial string of bidirectional light emittingdiodes to limit current flow.